Knives in cutting machines

ABSTRACT

The knife for a cutting machine comprises a plate having one bevelled cutting edge and a plurality of grooves formed at right angles to the cutting edge in the face of the knife which is not bevelled thereby providing a crenellated cutting edge.

United States Patent [1113,584,668

[72] Inventor Richard E. G. Neville [56] References Cied I N 222 31 5 England UNITED STATES PATENTS 955 Febn 1969 386,183 7/1888 Brooks /355 Patented 1971 2,835,299 5/1958 Pollmann 146/119 Assignee AMI. incorporated 3,186,277 6/1965 Brunner 83/355 New York, N.Y. FOREIGN PATENTS 125,505 9/1947 Australia 146/129(.1) 54,006 10/1890 Germany 146/129 [54] KNIVES [N CUTTING MACHINES Primary Examiner-Willie G. Abercrombie 7 Chins, 9 Drawing Figs Attorneys-George W. Price and E11 Weiss 146/129 ABSTRACT: The knife for a cutting machine comprises a [51] Int. Cl i A0ld 55/18 plate having one bevelled cutting edge and a plurality of [50] Field of Search 146/129, grooves formed at right angles to the cutting edge in the face 129.1, 78.2, 117, 118-- 120; 30/355; 83/636, 694, of the knife which is not bevelled thereby providing a crenel- 355,341 lated cutting edge.

PATENTEllJumslsn 3 5 4 5 sum 1 UF 3 INVENTOR RICHARD E. G. NEVlLLE PATENTEDJUNI 51971 SHEET 2 UF 3 INVENTOR RICHARD E G NEVILLE PATENTEUJUNISIQ?! 3 5 4 5 sum 3 BF 3 INVENTOR RICHARD 5c. NEVILLE BY I M-ZJOR KNIVES IN CUTTING MACHINES BACKGROUND TO INVENTION This invention relates to a knife for a cutting machine particularly but not solely for cutting tea.

In the Napier Ford method for the processing of tea, the freshly plucked green leaves are cut into shreds to initiate the fermentation. The resultant product is known in the trade as Legg cut tea or fresh cut tea."

The machine used for cutting the tea is of the well-known type used for cutting tobacco leaf, in which the leaf is fed into a convergent throat of rectangular cross section formed by two parallel plates and two converging conveyor bands or by two parallel plates and two converging roller conveyors. At the convergent end of the throat is a mouthpiece. The leaf is fed into the throat at the divergent end and the conveyor bands or rollers are driven through the mouthpiece, where the leaf is cut as it issues from the mouthpiece either by a single knife caused to reciprocate across the mouthpiece or by one or more knives arranged in a holder which rotates on an axis either at right angles or parallel to the axis of the throat, so that the cutting edge of the knife or knives are caused to pass across the mouthpiece. The convergence of the throat compresses the leaf sufficiently so that it may be cut and not pulled from the mouthpiece. One of the two band or roller conveyors is free to move and pressure is applied to it so that the compression of the leaf can be regulated. The width of cut of the shreds can be adjusted by altering the conveyor speed and hence the distance the compressed leaf is fed through the mouthpiece between cuts by the knife or knives.

Oxidation (called fermentation in the trade) starts at the severed edge of the leaf and proceeds inwards. In order to achieve uniform fermentation a line width of cut is preferred, usually between 30 and 80 cuts per inch. It was found that the resultant shreds were not easily handled, in particular they could not be uniformly spread on the tray-type driers used for stopping the fermentation. This type of drier depends on a uniform layer for efficient operation. To make the shreds more handleable and of more acceptable size for the tea blenders, the leaf is first fed to one cutter and the resultant shreds turned through 90 and fed to a second cutter to crosscut the original shreds.

The disadvantages of cutting successively on two cutters are that the leaf is twice subjected to pressure so that more of the flavor-containing natural juices and volatiles are squeezed out and lost; that not all the shreds are turned through 90 so that the product is not uniform and that where a coarse cut of 4 to 8 cuts per inch is used for the first cut, uncut pieces are more easily pulled out during the second line out and these ferment only at the edges.

The object of this invention is a new knife which can simultaneously produce a first cut and a crosscut with a single passage of the knife through the leaf. With this new knife, the leaf only passes once through a cutting machine avoiding the second compression and producing a very much more uniform cut.

SUMMARY OF INVENTION According to the invention we provide a knife for a cutting machine comprising a plate having one bevelled cutting edge and a plurality of grooves formed at right angles to the cutting edge in the face of the knife which is not bevelled thereby providing a crenellated cutting edge. The knife is known as a crosscutting knife.

BRIEF DESCRIPTION OF DRAWINGS constructional forms of the invention will now be described by way of examples with reference to the accompanying drawings in which:

. FIG. I shows in end elevation part of a knife having grooves of rectangular cross section,

FIG. 2 shows the knife in plan,

FIG. 3 is a section on A-A of FIG. 2,

FIG. 4 shows in end elevation part of a further knife having bevelled grooves,

FIG. 5 is a plan view,

FIG. 6 is a section on 8-8 of the knife shown in FIG. 5,

FIG. 7 is a side elevation of a reciprocating tea-cutting machine with parts removed for clarity,

FIG. 8 is a side elevation of a rotary cutting machine, and

FIG. 9 is an axial elevation of the drum carrying the knives.

DESCRIPTION OF PREFERRED EMBODIMENTS A conventional knife consists of a rectangular plate of hardened steel with one edge bevelled by grinding to produce a straight line cutting edge.

The new knife 10 as shown in FIGS. 1 to 3 is shaped in the manner of a conventional knife with rectangular section grooves 11 cut at right angles to the cutting edge, in the face of the knife which is not bevelled, at a pitch equal to 1% to 2 times the groove width and repeated so as to cover the entire cutting edge. In order to obtain equal length of cut tea the width of the grooves is equal to the space between them. The effect of the grooves is to produce a crenellated cutting edge 12 with alternate short cutting edges 12a and 121) on two common lines spaced apart. The knife is sharpened by grinding the bevel in the same way as a conventional knife, the two lines of cutting edges being sharpened simultaneously. The grooves are typically one-eighth inch to three-eighths inch wide, one thirty-second inch deep and sharp cornered. A particular knife suitable for cutting the leaf has grooves one-eighth inch in width and spaced apart by one-eighth inch. The grooves are 0.045 inch deep and the bevel ground 18 to the grooved face of the knife.

FIGS. 4 to 6 show an alternative form of knife I3 having grooves 14 which are undercut or dovetailed at 15. Undercutting has the effect of making the edges sharper than in the case of rectangular grooves.

The dimensions in a particular example the same as those in the knife have rectangular section grooves. However, the undercut angle may be to the bottom of the groove. In either example the bevelled edge may be flat or have a part cylindrical surface.

The knives of the two examples may be used in a reciprocating single-knife cutting machine ofthe kind shown in FIG. 6 or in the rotary cutter as shown in FIGS. 7 and $5.

The reciprocating machine of FIG. 6 comprises a conveyor 20 which feeds the leaf towards a mouthpiece 21 and a drum 22 through which the leaf L is compressed. A plurality of rollers 23 (or an upper conveyor as described above) form a divergent throat with the conveyor 26.

The knife 10 or 13 is clamped by a. gripper plate 24 which is driven via a connecting rod 25 and. an eccentric 26 by a flywheel 27. The knife is set at a slight angle to the gripper plate, with the grooved face towards the mouthpiece, in which case the groove depth should preferably be greater than the maximum depth of cut to be used. The depth of cut may be altered by varying the conveyor speed in relation to the reciprocating action of the knife.

As the knife passes across the mouthpiece the leading cutting edges 12a will effect a cut (a chiseiing action) along one intermittent line and the offset edges 12b will out along a further intermittent line. The corners of the grooves extending through to the bevelled edge of the knife will effect a crosscut.

A rotary machine is shown in FIGS. 8 and 9. Leaf tea is fed into the space 32 between two converging conveyor belts 34 and 36 which carry the tea to a mouthpiece 38 and at the same time compress it so that it is driven through the mouthpiece as a plug. As the plug emerges it is shredded by knife It) or 13 carried in holders 42 on a drum 44 which rotates about an axis 46 in bearings carried by arms 47. The cutter edges of the knives all lie on an imaginary cylindrical surface. The knives are arranged in this example with the grooves away from the mouthpiece.

With the knives in the fixed condition a continuous grinding can be effected by a grinding wheel 49 which has a drive mechanism for traversing the knives as they rotate. The bevelled surface will be part cylindrical in this case. Altematively the knives may be brought in turn to a fixed grinding position and ground one at a time by a grinding wheel of which the normal to the grinding face at the point of contact with the knife does not pass through the drum axis. Here the bevelled surface is flat but raked in relation to its cylindrical path or may be part cylindrical.

lclaim:

1. A knife for a cutting machine comprising a plate having one bevelled cutting edge and a plurality of grooves rectangular in cross section and formed at right angles to the cutting edge in the face of the plate which is not bevelled thereby providing a crenellated cutting edge.

2. The structure of claim 2 wherein the grooves are undercut at their sides to form a dovetail cross section.

3. The structure of claim 3 wherein the width of the grooves are each equal to the space between adjacent grooves.

4. The structure of claim 4, wherein the bevelled surface is part cylindrical.

5. The structure of claim 5 including a conveyor for driving material to be cut to a cutting position, means for effecting compression of said material at said cutting position and reciprocating mechanism for driving said knife.

6. The structure of claim 5 including a conveyor for driving material to be cut to a cutting position, means for effecting compression of said material at said cutting position, and a rotary drum having drive means therefor coupled to support a knife.

7. The structure of claim 9 including a grinding wheel positioned to contact the knife to provide the knife with a raked cutting edge. 

1. A knife for a cutting machine comprising a plate having one bevelled cutting edge and a plurality of grooves rectangular in cross section and formed at right angles to the cutting edge in the face of the plate which is not bevelled thereby providing a crenellated cutting edge.
 2. The structure of claim 2 wherein the grooves are undercut at their sides to form a dovetail cross section.
 3. The structure of claim 3 wherein the width of the grooves are each equal to the space between adjacent grooves.
 4. The structure of claim 4, wherein the bevelled surface is part cylindrical.
 5. The structure of claim 5 including a conveyor for driving material to be cut to a cutting position, means for effecting compression of said material at said cutting position and reciprocating mechanism for driving said knife.
 6. The structure of claim 5 including a conveyor for driving material to be cut to a cutting position, means for effecting compression of said material at said cutting position, and a rotary drum having drive means therefor coupled to support a knife.
 7. The structure of claim 9 including a grinding wheel positioned to contact the knife to provide the knife with a raked cutting edge. 